The present invention relates to ultrasonic motors and electronic apparatus provided with an ultrasonic motor wherein a moving member is driven through friction using a vibrating wave generated by utilizing the piezo-electric effects of a piezo-electric element.
Conventionally, an ultrasonic motor has a constitution in which projections 107 are provided on a vibrating member 101 near every other one of the boundaries of electrode patterns 104a and 104b to transmit power to a moving member, as is shown in FIGS. 29 and 30. For example, an ultrasonic motor of such a constitution is disclosed in the official report as Japanese Patent laid open JP-A-63-69472 (1988).
An ultrasonic motor of a constitution in which projections are provided on a vibrating member near every other one of the boundaries of the electrode patterns to transmit power to a moving member can be driven with a single driving signal, and in this regard has the advantage over conventional ultrasonic motors of the traveling wave type which are common. However, seeing the positions of the projections on the vibrating member within a cycle of a wavelength of a wave generated in the vibrating member, the projections are positioned with offset, causing imbalance in the vibrating member. Accordingly, vibration characteristics of the vibrating member are easily affected by changes in temperature, driving voltage or the conditions of pressure applied to the moving member. As a result, there has been a problem in that stable driving of the motor is rather difficult and thus the control circuit for the motor has become very complicated.